1. Field of the Invention
The present invention relates to a method and apparatus for testing wire, that is for measuring deviations in wire and more particularly, for measuring deviations in the wire thickness and wire roll of trolley wire.
2. Description of Prior Art
Trolley wires have to be tested periodically in a effort to disclose areas subject to failure. One type of test includes testing the wear of the trolley wire, that is testing the trolley wire for a minimum wire thickness. The results of the test prompt the replacement of the trolley wire prior to failure and establishes a wire wear pattern which is useful in projecting a budget for the future replacement of the trolley wire. Trolley wires are also tested upon the completion of their installation to determine if the installation has been conducted in compliance with the contract specifications which require that the trolley wire not have any roll or twist. A roll or twist in the trolley wire will cause premature wear of the trolley wire.
Trolley wires are currently tested using unsophisticated methods. One method currently in use involves the visual inspection of the trolley wire. This is accomplished through individuals who walk along the right of way beneath the trolley wire visually inspecting the trolley wire from the ground surface for obvious wear or damage. Since the height of the trolley wire ranges from fourteen feet to twenty-four feet, this type of inspection offers very limited results. Another method requires a physical inspection of the trolley wire with the use of micrometers or calipers. This method is very time consuming and laborious. Moreover, there are areas of limited access. One such area where access is limited is adjacent the hanger where a rigid segment of trolley wire exists. This is an area of accelerated wear. A more accurate and efficient method and apparatus would prove to be of greater value then the methods currently in use.
U.S. Pat. No. 4,586,379 issued may 6, 1986 to Frederick R. Burkhardt, Jr. discloses a remote controlled ultrasonic transducer assembly which includes a platform movable along an arm projecting from a carriage on a track around a pipe. The assembly includes a pipe contacting surface which lies close to the pipe and a universal joint which is maneuvered to cause the assembly to move circumferentially around the pipe, pressing the assembly against the pipe and moving along the weld controlling the angle of the transducer relative to the direction of the movement. A couplant fluid is continuously supplied to the pipe surface under test to couple the pipe surface and the ultrasonic transducer assembly. U.S. Pat. No. 4,523,468 issued Jun. 18, 1985 to Thomas Derkacs et al. discloses a system including an array of ultrasonic transducers which transmit circumferentially around a cylindrical object and a set of ultrasonic transducers which transmit axially around a cylindrical object. A trigger pulse triggers a single transducer of each set separately while the other transducers operate in a receiving mode to receive a reflected wave. A central processor unit uses a measurement of the time of flight relationship of the ultrasonic signal traveling from the transmitting transducer to the defect and from the defect to the receiving transducer to triangulate the location of the reflective defect. U.S. Pat. No. 4,375,165 issued Mar. 1, 1983 to Arie de Sterke discloses an assembly which circumferentially inspects the welded joints in a pipeline. A set of ultrasonic probes direct ultrasonic waves into and receive ultrasonic waves from the interior surface of the pipe in order to measure the pipe diameter, the wall thickness, and inspect the welded joint. The system is a mobile system which includes a multicrystal switch controlled by a multichannel ultrasonic device for transmitting ultrasonic waves into the pipe material.